Convert 2 similarly-looking German characters of different kinds to same ASCII string in PHP

Question

I have these two strings:

$str1 = \'Ö\';
$str2 = \'Ö\';
$e1 = mb_detect_encoding($str1);
$e2 = mb_detect_encoding($str2);
var_dump($str1);
var_dump($str2);
         


        

Answer 1

Extending Andreas's answer. These characters are letter + combining diaeresis(U-0308). I was able to search and replace them to standard umlauts, then replace with whatever is needed. This is the fuction I've used to replace them:

function convertToUmlauts($str) {
    $srp_array = ['Ö' => 'Ö', 'Ä' => 'Ä', 'Ü' => 'Ü', '̈a' => 'ä', 'ö' => 'ö', 'ü' => 'ü'];
    return strtr($str, $srp_array);
}

Answer 2

You could first convert your input to utf-8 using iconv and then apply your conversion to ASCII. To detect the current encoding you can use mb_detect_encoding.

$aUTF8 = iconv(mb_detect_encoding($a, 'UTF-8, ISO-8859-1', true), 'UTF-8', $a);
$bUTF8 = iconv(mb_detect_encoding($b, 'UTF-8, ISO-8859-1', true), 'UTF-8', $b);

$aASCII = iconv("utf-8", "ascii//TRANSLIT", $aUTF8);
$bASCII = iconv("utf-8", "ascii//TRANSLIT", $bUTF8);

Please note that you might have to add additional encodings to the encoding list of mb_detect_encoding.

Answer 3

These are two different forms to express the same letter in Unicode; one is the combination of an O with combining diereses, the other is the letter Ö. Unicode allows either variant to express "Ö".

To normalize that into your preferred variant, use Normalizer::normalize:

$str = Normalizer::normalize('Ö', Normalizer::FORM_C);

Likely you want Form C, which will converge on "Ö" (the single letter form). If you prefer "O" + combining diereses, use Form D instead.